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撰写（费用委托）

当您要执行智能合约时，您可以向 feepayer 发送**"交易 "，其中包括支付请求**。

从 Web3j 和 kaia 库（web3j-ext）中导入必要的类。

使用 Web3j 连接到 kaia 区块链并指定 URL

使用私钥创建发送方和付费方证书。

指定已部署合约的**地址

确定交易的gas价格和gas限额

从 credentials.getAddress() 获取发件人地址

获取发件人地址的 nonce

从 Kaia 网络获取链 ID

为交易参数初始化变量

创建gas供应商，并设定静态gas价格和gas限额

使用联系地址、Web3j 实例、凭据和gas提供商加载合约。 您可以通过该实例读写合约

在写入之前，获取合约中存储的当前数字

为调用方法 setNumber 设置合约参数

将交易类型定义为 FEE_DELEGATED_SMART_CONTRACT_EXECUTION

创建原始交易

使用 "KlayTransactionEncoder.signMessage "以**发送方的身份签署交易。

使用 "KlayTransactionEncoder.signMessageAsFeePayer "将交易签署为付费方。

向 kaia 网络发送已签署的交易

短暂延迟以确保交易完成

写入后，获取存储在合约中的更新号

关闭 Web3j 实例

WriteContractWithFeeDelegationExample.java

package org.web3j.example.contracts;

import java.io.IOException;

import java.math.BigInteger;

import org.web3j.crypto.KlayCredentials;

import org.web3j.crypto.KlayRawTransaction;

import org.web3j.crypto.KlayTransactionEncoder;

import org.web3j.crypto.transaction.type.TxType;

import org.web3j.crypto.transaction.type.TxTypeFeeDelegatedSmartContractExecution;

import org.web3j.crypto.transaction.type.TxType.Type;

import org.web3j.tx.response.PollingTransactionReceiptProcessor;

import org.web3j.tx.response.TransactionReceiptProcessor;

import org.web3j.example.keySample;

import org.web3j.protocol.core.DefaultBlockParameterName;

import org.web3j.protocol.core.methods.request.Transaction;

import org.web3j.protocol.core.methods.response.EthChainId;

import org.web3j.protocol.core.methods.response.EthSendTransaction;

import org.web3j.protocol.http.HttpService;

import org.web3j.protocol.kaia.Web3j;

import org.web3j.utils.Numeric;

import org.web3j.protocol.kaia.core.method.response.KlayCallResponse;

import org.web3j.protocol.kaia.core.method.response.TransactionReceipt;

import org.web3j.tx.gas.StaticGasProvider;

import org.web3j.abi.FunctionEncoder;

import org.web3j.abi.datatypes.Function;

import org.web3j.abi.datatypes.Uint;

import java.util.Arrays;

import java.util.Collections;

public class WriteContractWithFeeDelegationExample {

/**

* @throws Exception

*

*/

public static void run() throws Exception {

Web3j web3j = Web3j.build(new HttpService(keySample.BAOBAB_URL));

KlayCredentials credentials = KlayCredentials.create(keySample.LEGACY_KEY_privkey);

KlayCredentials credentials_feePayer = KlayCredentials.create(keySample.LEGACY_KEY_FEEPAYER_privkey);

String contractAddr = "0x95Be48607498109030592C08aDC9577c7C2dD505";

BigInteger GAS_PRICE = BigInteger.valueOf(50000000000L);

BigInteger GAS_LIMIT = BigInteger.valueOf(6721950);

String from = credentials.getAddress();

BigInteger nonce = web3j.ethGetTransactionCount(from, DefaultBlockParameterName.LATEST).send()

.getTransactionCount();

EthChainId EthchainId = web3j.ethChainId().send();

long chainId = EthchainId.getChainId().longValue();

BigInteger value = BigInteger.ZERO;

StaticGasProvider gasProvider = new StaticGasProvider(GAS_PRICE, GAS_LIMIT);

Counter counter = Counter.load(contractAddr, web3j, credentials.convertToCredentials(), gasProvider);

// Get number before Contract Write

System.out.println("number before : " + counter.number().send());

// Contract Write (Set number with setNumber function)

Function function = new Function("setNumber", // Function name

Arrays.asList(new Uint(BigInteger.valueOf(50))), // Function input parameters

Collections.emptyList()); // Function returned parameters

String txData = FunctionEncoder.encode(function);

byte[] payload = Numeric.hexStringToByteArray(txData);

TxType.Type type = Type.FEE_DELEGATED_SMART_CONTRACT_EXECUTION;

KlayRawTransaction raw = KlayRawTransaction.createTransaction(

type,

nonce,

GAS_PRICE,

GAS_LIMIT,

contractAddr,

value,

from,

payload);

// Sign as sender

byte[] signedMessage = KlayTransactionEncoder.signMessage(raw, chainId, credentials);

// Sign same message as Fee payer

signedMessage = KlayTransactionEncoder.signMessageAsFeePayer(raw, chainId, credentials_feePayer);

String hexValue = Numeric.toHexString(signedMessage);

web3j.ethSendRawTransaction(hexValue).send();

try {

Thread.sleep(2000);

} catch (Exception e) {

System.out.println(e);

}

// Get number after Contract Write

System.out.println("number after : " + counter.number().send());

web3j.shutdown();

}

}

output

❯ java WriteContractWithFeeDelegationExample.java

number before : 298

number after : 50